U.S. patent number 7,935,643 [Application Number 12/604,332] was granted by the patent office on 2011-05-03 for stress management for tensile films.
This patent grant is currently assigned to Applied Materials, Inc.. Invention is credited to Nitin K. Ingle, Jingmei Liang, Anjana M. Patel, Shankar Venkataraman.
United States Patent |
7,935,643 |
Liang , et al. |
May 3, 2011 |
Stress management for tensile films
Abstract
The formation of a gap-filling silicon oxide layer with reduced
tendency towards cracking is described. The deposition involves the
formation of a flowable silicon-containing layer which facilitates
the filling of trenches. Subsequent processing at high substrate
temperature causes less cracking in the dielectric film than
flowable films formed in accordance with methods in the prior art.
A compressive liner layer deposited prior to the formation of the
gap-filling silicon oxide layer is described and reduces the
tendency for the subsequently deposited film to crack. A
compressive capping layer deposited after a flowable
silicon-containing layer has also been determined to reduce
cracking. Compressive liner layers and compressive capping layers
can be used alone or in combination to reduce and often eliminate
cracking. Compressive capping layers in disclosed embodiments have
additionally been determined to enable an underlying layer of
silicon nitride to be transformed into a silicon oxide layer.
Inventors: |
Liang; Jingmei (San Jose,
CA), Patel; Anjana M. (San Jose, CA), Ingle; Nitin K.
(Santa Clara, CA), Venkataraman; Shankar (Santa Clara,
CA) |
Assignee: |
Applied Materials, Inc. (Santa
Clara, CA)
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Family
ID: |
43901011 |
Appl.
No.: |
12/604,332 |
Filed: |
October 22, 2009 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20110034035 A1 |
Feb 10, 2011 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61231729 |
Aug 6, 2009 |
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Current U.S.
Class: |
438/761;
257/E21.279; 438/758; 257/E21.273 |
Current CPC
Class: |
H01L
21/76834 (20130101); H01L 21/76829 (20130101); H01L
21/0217 (20130101); H01L 21/02304 (20130101); H01L
21/02164 (20130101); H01L 21/76837 (20130101); H01L
21/02362 (20130101); H01L 21/02326 (20130101); C23C
16/56 (20130101); H01L 21/3185 (20130101); C23C
16/452 (20130101); H01L 21/02274 (20130101); H01L
21/31608 (20130101); C23C 16/401 (20130101) |
Current International
Class: |
H01L
21/31 (20060101); H01L 21/469 (20060101) |
Field of
Search: |
;438/761-790,424
;257/E21.273-E21.279,E21.548 |
References Cited
[Referenced By]
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EP |
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01241826 |
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JP |
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10-2004-0091978 |
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Nov 2004 |
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KR |
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10-2005-0094183 |
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Sep 2005 |
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KR |
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WO 02/077320 |
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WO |
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WO 03/066933 |
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WO |
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WO |
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WO |
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WO 2007/140424 |
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Dec 2007 |
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WO |
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Other References
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Nano Sciences Center, Research Briefs, 2005, pp. 42-43. cited by
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Device Applications," Georgia Institute of Technology, Doctor of
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Primary Examiner: Ghyka; Alexander G
Assistant Examiner: Mustapha; Abdulfattah
Attorney, Agent or Firm: Kilpatrick, Townsend and
Stockton
Claims
What is claimed is:
1. A method of forming a silicon oxide layer on a substrate
containing a trench, the method comprising: transferring the
substrate into a substrate processing region in a substrate
processing chamber; flowing a plasma precursor into a remote plasma
region to form plasma effluents; combining the plasma effluents
with a flow of a silicon-containing precursor in the substrate
processing region, wherein the flow of the silicon-containing
precursor has not been excited by a plasma; forming a
silicon-and-nitrogen-containing layer on the substrate and in the
trench; forming a compressive capping layer over the
silicon-and-nitrogen-containing layer; and heating the substrate in
an oxygen-containing atmosphere to convert the carbon-free
silicon-and-nitrogen containing layer to the silicon oxide
layer.
2. The method of claim 1 further comprising an operation of forming
a compressive liner layer prior to the operation of forming the
silicon-and-nitrogen-containing layer on the substrate.
3. The method of claim 1 further comprising an operation of curing
the silicon-and-nitrogen-containing layer in an ozone-containing
atmosphere prior to the operation of forming the compressive
capping layer.
4. The method of claim 1 wherein the silicon-containing precursor
comprises a silicon-and-nitrogen-containing precursor and the
plasma effluents comprise a radical-nitrogen precursor.
5. The method of claim 4, wherein the
silicon-and-nitrogen-containing precursor comprises at least one of
H.sub.2N(SiH.sub.3), HN(SiH.sub.3).sub.2, and N(SiH.sub.3).sub.3
and the plasma precursor comprises at least one of N.sub.2O, NO,
NO.sub.2, NH.sub.4OH, NH.sub.3, N.sub.2 and H.sub.2.
6. The method of claim 1, wherein the oxygen-containing atmosphere
comprises at least one of O.sub.2, O.sub.3 and H.sub.2O.
7. The method of claim 1, wherein the trench has a width of about
50 nm or less.
8. The method of claim 1, wherein the remote plasma region is
within the substrate processing chamber and separated from the
substrate processing chamber by a showerhead.
9. The method of claim 1, wherein the compressive capping layer is
deposited using one of a furnace, PECVD, LP-CVD and HDP-CVD.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is related to U.S. Prov. Pat. App. Ser. No.
61/231,729, filed Aug. 6, 2009, and titled "FORMATION OF SILICON
OXIDE USING NON-CARBON FLOWABLE CVD PROCESSES," the entire contents
of which is herein incorporated by reference for all purposes.
BACKGROUND OF THE INVENTION
Semiconductor device geometries have dramatically decreased in size
since their introduction several decades ago. Modern semiconductor
fabrication equipment routinely produces devices with 250 nm, 180
nm, and 65 nm feature sizes, and new equipment is being developed
and implemented to make devices with even smaller geometries. The
decreasing feature sizes result in structural features on the
device having decreased spatial dimensions. The widths or gaps and
trenches on the device narrow to a point where the aspect ratio of
gap depth to its width becomes high enough to make it challenging
to fill the gap with dielectric material. The depositing dielectric
material is prone to clog at the top before the gap completely
fills, producing a void or seam in the middle of the gap.
Over the years, many techniques have been developed to avoid having
dielectric material clog the top of a gap, or to "heal" the void or
seam that has been formed. One approach has been to start with
highly flowable precursor materials that may be applied in a liquid
phase to a spinning substrate surface (e.g., SOG deposition
techniques). These flowable precursors can flow into and fill very
small substrate gaps without forming voids or weak seams. However,
once these highly flowable materials are deposited, they have to be
hardened into a solid dielectric material.
In many instances, the hardening process includes a heat treatment
to remove carbon and hydroxyl groups from the deposited material to
leave behind a solid dielectric such as silicon oxide.
Unfortunately, the departing carbon and hydroxyl species often
leave behind pores in the hardened dielectric that reduce the
quality of the final material. In addition, the hardening
dielectric also tends to shrink in volume, which can leave cracks
and spaces at the interface of the dielectric and the surrounding
substrate. In some instances, the volume of the hardened dielectric
can decrease by 40% or more.
Thus, there is a need for new deposition processes and materials to
form dielectric materials on structured substrates without
generating voids, seams, or both, in substrate gaps and trenches.
There is also a need for materials and methods of hardening
flowable dielectric materials with fewer pores and less shrinkage
as well as accommodating the shrinkage which still occurs. This and
other needs are addressed in the present application.
BRIEF SUMMARY OF THE INVENTION
The formation of a gap-filling silicon oxide layer with reduced
tendency towards cracking is described. The deposition involves the
formation of a flowable silicon-containing layer which facilitates
the filling of trenches. Subsequent processing at high substrate
temperature causes less cracking in the dielectric film than
flowable films formed in accordance with methods in the prior art.
A compressive liner layer deposited prior to the formation of the
gap-filling silicon oxide layer is described and reduces the
tendency for the subsequently deposited film to crack. A
compressive capping layer deposited after a flowable
silicon-containing layer has also been determined to reduce
cracking. Compressive liner layers and compressive capping layers
can be used alone or in combination to reduce and often eliminate
cracking. Compressive capping layers in disclosed embodiments have
additionally been determined to enable an underlying layer of
silicon nitride to be transformed into a silicon oxide layer.
In one embodiment, a method of forming a silicon oxide layer on a
substrate containing a trench includes transferring the substrate
into a substrate processing chamber; forming a compressive lining
layer on the substrate and in the trench; forming a dielectric
layer on the substrate and in the trench, wherein the dielectric
layer is initially flowable; and curing the dielectric layer.
In yet another embodiment, a method of forming a silicon oxide
layer on a substrate containing a trench includes transferring the
substrate into a substrate processing region in a substrate
processing chamber; flowing a plasma precursor into a remote plasma
region to form plasma effluents; combining the plasma effluents
with a flow of a silicon-containing precursor in the substrate
processing region, wherein the flow of the silicon-containing
precursor has not been excited by a plasma; forming a
silicon-and-oxygen-containing layer on the substrate and in the
trench; forming a compressive capping layer over the
silicon-and-oxygen-containing layer; and curing the
silicon-and-oxygen-containing layer.
In yet another embodiment, a method of forming a silicon oxide
layer on a substrate containing a trench includes transferring the
substrate into a substrate processing region in a substrate
processing chamber; flowing a plasma precursor into a remote plasma
region to form plasma effluents; combining the plasma effluents
with a flow of a silicon-containing precursor in the substrate
processing region, wherein the flow of the silicon-containing
precursor has not been excited by a plasma; forming a
silicon-and-nitrogen-containing layer on the substrate and in the
trench; forming a compressive capping layer over the
silicon-and-nitrogen-containing layer; and heating the substrate in
an oxygen-containing atmosphere to convert the carbon-free
silicon-and-nitrogen containing layer to the silicon oxide
layer.
Additional embodiments and features are set forth in part in the
description that follows, and in part will become apparent to those
skilled in the art upon examination of the specification or may be
learned by the practice of the disclosed embodiments. The features
and advantages of the disclosed embodiments may be realized and
attained by means of the instrumentalities, combinations, and
methods described in the specification.
BRIEF DESCRIPTION OF THE DRAWINGS
A further understanding of the nature and advantages of the present
invention may be realized by reference to the remaining portions of
the specification and the drawings wherein like reference numerals
are used throughout the several drawings to refer to similar
components. In some instances, a sublabel is associated with a
reference numeral and follows a hyphen to denote one of multiple
similar components. When reference is made to a reference numeral
without specification to an existing sublabel, it is intended to
refer to all such multiple similar components.
FIG. 1 is a flowchart illustrating selected steps for making a
multi-layer silicon oxide film according to disclosed
embodiments.
FIG. 2 is another flowchart illustrating selected steps for forming
a multi-layer silicon oxide film according to disclosed
embodiments.
FIG. 3 is another flowchart illustrating selected steps for forming
a multi-layer silicon oxide film according to disclosed
embodiments.
FIG. 4 shows a substrate processing system according to disclosed
embodiments.
FIG. 5A shows a substrate processing chamber according to disclosed
embodiments.
FIG. 5B shows a showerhead of a substrate processing chamber
according to disclosed embodiments.
DETAILED DESCRIPTION OF THE INVENTION
The formation of a gap-filling silicon oxide layer with reduced
tendency towards cracking is described. The deposition involves the
formation of a flowable silicon-containing layer which facilitates
the filling of trenches. Subsequent processing at high substrate
temperature causes less cracking in the dielectric film than
flowable films formed in accordance with methods in the prior art.
A compressive liner layer deposited prior to the formation of the
gap-filling silicon oxide layer is described and reduces the
tendency for the subsequently deposited film to crack. A
compressive capping layer deposited after a flowable
silicon-containing layer has also been determined to reduce
cracking. Compressive liner layers and compressive capping layers
can be used alone or in combination to reduce cracking. Compressive
capping layers in disclosed embodiments have additionally been
determined to enable an underlying layer of silicon nitride to be
transformed into a silicon oxide layer.
Without binding the coverage of the claims to hypothetical process
mechanisms, inclusion of either a compressive liner layer and/or a
compressive capping layer is thought to stabilize the flowable
gap-filling silicon oxide layer during and after subsequent
processing. Flowable films may require curing either as a distinct
curing step or as a natural by-product of heating a film stack
including the gap-filling film during subsequent processing. The
gap-filling film is typically reduced in mass through outgassing
and develops tensile stress. Such a layer may be referred to herein
as a tensile layer. The compressive liner layer is thought to
stabilize trenches prior to the filling of the gap with the
flowable gap-filling silicon oxide layer. The presence of a
compressive liner layer and/or a compressive capping layer also may
serve to physically adhere to and stabilize the gap-filling layer.
The physical curvature of the substrate as a whole may also be
mitigated by the presence of the compressive layers, reducing the
curvature imparted during curing of the gap-filling film reducing
its tensile stress during subsequent processing. Additional details
about the methods and systems of forming the silicon oxide layer
will now be described.
Exemplary Silicon Oxide Formation Processes
FIG. 1 is a flowchart showing selected steps in methods 100 of
making silicon oxide films according to embodiments of the
invention. The method 100 includes depositing a silicon oxide liner
layer by high-density plasma CVD (HDP-CVD) on a substrate 102.
HDP-CVD is an exemplary method of forming a silicon oxide layer
which exhibits tensile stress especially upon cooling the substrate
following the composite deposition process. Other methods may be
used (e.g. PECVD, LP-CVD or furnace oxide) to form the silicon
oxide compressive lining layer which would be similarly effective
at inhibiting the formation of cracks in the completed film stack
during and following curing/heating of the film stack. The
compressive lining layer may also be silicon nitride grown by a
variety of techniques including HDP-CVD, PECVD, LP-CVD and by using
a high temperature furnace.
The method 100 further includes providing a carbon-free silicon
precursor to a reaction chamber 104. The carbon-free silicon
precursor may be, for example, a silicon-and-nitrogen precursor, a
silicon-and-hydrogen precursor, or a silicon-nitrogen-and-hydrogen
containing precursor, among other classes of silicon precursors.
Specific examples of these precursors may include silyl-amines such
as H.sub.2N(SiH.sub.3), HN(SiH.sub.3).sub.2, and
N(SiH.sub.3).sub.3, among other silyl-amines. These silyl-amines
may be mixed with additional gases that may act as carrier gases,
reactive gases, or both. Examples of the these additional gases may
include H.sub.2, N.sub.2, NH.sub.3, He, and Ar, among other gases.
Examples of carbon-free silicon precursors may also include silane
(SiH.sub.4) either alone or mixed with other silicon (e.g.,
N(SiH.sub.3).sub.3), hydrogen (e.g., H.sub.2), and/or nitrogen
(e.g., N.sub.2, NH.sub.3) containing gases.
A radical-nitrogen precursor may also be provided to the reaction
chamber 106. The radical-nitrogen precursor comprises plasma
effluents created by exciting a nitrogen-containing precursor in a
plasma and exemplary nitrogen-containing precursors may include
N.sub.2O, NO, NO.sub.2, NH.sub.4OH, NH.sub.3 and N.sub.2. The
radical-nitrogen precursor may be a nitrogen-radical containing
species that was generated outside the reaction chamber from a more
stable nitrogen precursor. For example, a stable nitrogen precursor
compound such as those listed above may be activated in a plasma
unit outside the reaction chamber to form the radical-nitrogen
precursor, which is then transported into the reaction chamber. The
radical-nitrogen precursor produced may include one or more of .N,
.NH, .NH.sub.2, etc., and may also be accompanied by ionized
species formed in the plasma. In other embodiments, the
radical-nitrogen precursor is generated in a section of the
reaction chamber partitioned from the substrate processing region
where the precursors mix and react to deposit the
silicon-and-nitrogen layer on a deposition substrate (e.g., a
semiconductor wafer). The radical-nitrogen precursor may also be
accompanied by a carrier gas such as hydrogen (H.sub.2), helium,
etc.
In the reaction chamber, the unexcited carbon-free silicon
precursor and the radical-nitrogen precursor mix and react to
deposit a silicon-and-nitrogen containing film on the deposition
substrate 108 with trenches formed in its surface. Trenches may be
difficult to fill without forming voids or seams using less
flowable films produced with prior art gapfilling techniques such
as HDP-CVD. The trenches may have a height and width that define an
aspect ratio (AR) of the height to the width (i.e., HAW) that is
significantly greater than 1:1 (e.g., 5:1 or more, 6:1 or more, 7:1
or more, 8:1 or more, 9:1 or more, 10:1 or more, 11:1 or more, 12:1
or more, etc.). In many instances the high AR is due to small gap
widths that range from about 90 nm to about 22 nm or less (e.g.,
about 90 nm, 65 nm, 45 nm, 32 nm, 22 nm, 16 nm, etc.).
Unlike a conventional silicon nitride (Si.sub.3N.sub.4) film, the
deposited silicon-and-nitrogen containing film has flowable
characteristics allowing it to flow into narrow gaps trenches and
other structures on the deposition surface of the substrate.
Because the layer is flowable, it can fill gaps with high aspect
ratios without creating voids or weak seams around the center of
the filling material. For example, a depositing flowable material
is less likely to prematurely clog the top of the gap before it is
completely filled. This may help to reduce or eliminate voids which
remain in the middle of the gap.
The flowability may be due, at least in part, to a significant
hydrogen component in the deposited film. For example the deposited
film may have a silazane-type, Si--NH--Si backbone (i.e., a
Si--N--H film). Flowability may also result from short chained
polymers of the silazane type. When both the silicon precursor and
the radical-nitrogen precursor are carbon-free, the deposited
silicon-and-nitrogen-containing film is also substantially
carbon-free. Of course, "carbon-free" does not necessarily mean the
film lacks even trace amounts of carbon. Carbon contaminants may be
present in the precursor materials that find their way into the
deposited silicon-and-nitrogen-containing film. The amount of these
carbon impurities however are much less than would be found in a
silicon precursor having a carbon moiety (e.g., TEOS, TMDSO,
etc.).
Following the deposition of the silicon-and-nitrogen containing
layer, the deposition substrate may be introduced to a
oxygen-containing atmosphere 110. The deposition substrate may
remain in the reaction chamber when the oxygen-containing
atmosphere is introduced, or the substrate may be transferred to a
different chamber where the oxygen-containing atmosphere is
introduced. The oxygen-containing atmosphere may include one or
more oxygen containing gases such as molecular oxygen (O.sub.2),
ozone (O.sub.3), water vapor (H.sub.2O), and nitrogen-oxides (NO,
NO.sub.2, etc.), among other oxygen-containing gases. The
oxygen-containing atmosphere may also include radical oxygen and
hydroxyl species such as atomic oxygen (O), hydroxides (OH), etc.,
that may be generated remotely and transported into the substrate
chamber. Ions of oxygen-containing species may also be present.
The oxygen-containing atmosphere provides oxygen to convert the
silicon-and-nitrogen containing film into the silicon oxide
(SiO.sub.2) film 110. As noted previously, the lack of carbon in
the silicon-and-nitrogen containing film results in significantly
fewer pores formed in the final silicon oxide film. The net
shrinkage from deposition to anneal is reduced by depositing a
flowable silicon-and-nitrogen-containing film and converting to
silicon oxide as opposed to depositing a flowable
silicon-and-oxygen-containing film initially. During the conversion
process, the substrate temperature may range from about 25.degree.
C. to about 1100.degree. C. (e.g., about 200.degree. C., about
300.degree. C., about 400.degree. C., about 500.degree. C., about
600.degree. C., about 700.degree. C., about 800.degree. C., about
900.degree. C., about 1000.degree. C., etc.). In many cases, the
volume reduction is slight enough (e.g., about 15 vol. % or less)
to avoid post heat treatment steps to fill, heal, or otherwise
eliminate spaces that form in the gap as a result of the shrinking
silicon oxide. In an embodiment, the conversion may occur in two
parts. The two part conversion may include a low temperature ozone
cure to initiate the oxidation followed by a high temperature
anneal in an oxygen-containing environment.
The process of FIG. 1 describes a process wherein silicon oxide is
formed by first depositing a silicon-nitrogen-containing layer and
then converting the layer into silicon oxide. In other embodiments,
the deposited film is created by a radical-oxygen precursor
combining with a carbon-containing precursor which has not been
excited by a plasma. The deposited film would then be a
silicon-and-oxygen-containing film which may experience more
shrinkage during subsequent processing compared with a process
involving a silicon-and-nitrogen-containing film. Exemplary
carbon-containing precursor which does not pass through a plasma
may include TMOS, TriMOS, TEOS, OMCTS, HMDS, TMCTR, TMCTS, OMTS,
TMS, HMDSO and/or TMDSO. The radical-oxygen precursor comprises
plasma effluents created by exciting an oxygen-containing precursor
in a plasma and exemplary oxygen-containing precursors may include
O.sub.2, O.sub.3, N.sub.2O, NO, NO.sub.2, H.sub.2O.sub.2, H.sub.2O
and NH.sub.4OH. Cracking in films deposited in this manner may also
be reduced by using compressive lining and capping layers described
herein.
Embodiments may include multiple heating stages with different
temperatures and atmospheres. For example, a first heating stage
may be performed at a lower first temperature in an atmosphere that
includes steam (H.sub.2O), while a second heating stage may be
performed at a higher second temperature in a dry oxygen-containing
atmosphere which substantially lacks water vapor. A third heating
stage may also be conducted in a non-oxygen containing atmosphere
(e.g., dry N.sub.2, He, Ar, etc.).
Referring now to FIG. 2, another flowchart is shown illustrating
selected steps in methods 200 for forming a silicon oxide film in a
trench according to embodiments of the invention. The method 200
may include transferring a substrate with surface trenches into a
substrate processing region. The trenches may be used to dictate
the spacing and structure of device components (e.g., transistors)
formed on the substrate. The method 200 includes providing a
carbon-free silicon precursor to a reaction chamber 202.
Carbon-free silicon precursors were discussed in conjunction with
FIG. 1. A radical-nitrogen precursor is provided to the reaction
chamber 204 as described with reference to FIG. 1. Again,
alternative embodiments involve introducing an unexcited
carbon-containing precursor and a radical-oxygen precursor to form
a flowable silicon-and-oxygen-containing film which may exhibit
relatively more shrinkage during subsequent processing.
The carbon-free silicon precursor and the radical-nitrogen
precursor mix and react to deposit a flowable silicon and nitrogen
containing film on the deposition substrate (operation 206). The
flowable nature of the film facilitates the filling of the surface
trenches which may otherwise be difficult to completely fill using
less flowable films produced with prior art gapfilling techniques
such as HDP-CVD. Following the deposition, ozone is flowed into the
reaction region and the substrate is heated to a relatively low
temperature to initiate the oxidation and conversion of the
silicon-and-nitrogen-containing film into silicon dioxide
(operation 207).
A compressive capping layer is then deposited over the cured film
which contains silicon, oxygen and possibly nitrogen 208. One way
to deposit a capping layer under compressive strain is to deposit
it with HDP-CVD similar to the method of depositing the liner layer
of FIG. 1. The capping layer may be made thicker than the lining
layer since the trenches are largely filled at this point in the
process. Compressive capping layers are integrated into the process
flow and may enable the use of a thinner flowable film due to the
additional material provided by the compressive capping layer. In
some embodiments, the trench is not completely filled with the
gap-filling layer, in which case the compressive capping layer
fills some of the trench volume. Once again, other methods may be
used to produce the compressive capping layer (e.g. PECVD, LP-CVD,
furnace oxide) which would be similarly effective at inhibiting the
formation of cracks in the completed film stack during and
following annealing of the film stack. The compressive capping
layer may also be silicon nitride grown by a variety of techniques
including HDP-CVD, PECVD, LP-CVD and by using a high temperature
furnace.
Following the deposition of the compressive capping layer, the
deposition substrate may be introduced to a oxygen-containing
atmosphere 210. Again, the deposition substrate may remain in the
reaction chamber where the oxygen-containing atmosphere is
introduced, or the substrate may be transferred to a different
chamber where the oxygen-containing atmosphere is introduced. The
oxygen-containing atmosphere is as described with reference to FIG.
1. The oxygen-containing atmosphere provides oxygen to complete the
conversion of the silicon-and-nitrogen-containing film into silicon
oxide, a conversion which was initiated during the cure. The
conversion has been found to proceed despite the presence of the
compressive capping layer. Heating the cured silicon-and-nitrogen
containing layer in an oxygen-containing atmosphere again forms a
silicon oxide layer on the substrate and in the substrate gap. The
silicon oxide layer has fewer pores and less volume reduction than
similar layers formed with carbon-containing precursors that have
significant quantities of carbon present in the layer before the
heat treatment step. Compressive lining layers of FIG. 1 and
compressive capping layers of FIG. 2 may be combined, in disclosed
embodiments, to further protect a film stack from developing
cracks.
FIG. 3 is another flowchart illustrating selected steps in
additional exemplary methods 300 of making a silicon oxide film
according to embodiments of the invention. The methods 300 include
depositing a silicon oxide liner layer by high-density plasma CVD
(HDP-CVD) on a substrate 302. Other methods may be used (e.g.
PECVD, LP-CVD and furnace oxide) to form the compressive lining
layer provided the alternative methods form a compressive lining
layer to assist with a reduction in cracking during and following
curing and heating steps later in the processing sequence. The
methods 300 further include introducing a silicon-containing
precursor and a radical-oxygen precursor into a substrate
processing region 304.
The radical-oxygen precursor may be generated outside the plasma
CVD deposition chamber, for example, from a stable
oxygen-containing gas (e.g., molecular oxygen (O.sub.2), ozone
(O.sub.3), water vapor, hydrogen peroxide (H.sub.2O.sub.2), and
nitrogen oxides (e.g., N.sub.2O, NO.sub.2, etc.)). As with the
methods of FIGS. 1-2, mixtures of stable gases may also be used to
form the radical species. The radical oxygen may also be created in
a separated section of the reaction chamber partitioned from the
substrate processing region. In that separated section, the stable
oxygen-containing gas is excited by a plasma remote from the
substrate processing region. The partition may have apertures and
may be referred to as a showerhead herein.
The silicon-containing precursor is introduced directly into the
substrate processing region to avoid plasma excitation in disclosed
embodiments. The silicon-containing precursor may include
organo-silane compounds including TMOS, TriMOS, TEOS, OMCTS, HMDS,
TMCTR, TMCTS, OMTS, TMS, and HMDSO, among others. The
silicon-containing precursors may also include silicon compounds
that have no carbon, such as silane, disilane, etc. If the
deposited oxide film is a doped oxide film, dopant precursors may
also be used such as TEB, TMB, B.sub.2H.sub.6, TEPO, PH.sub.3,
P.sub.2H.sub.6, and TMP, among other boron and phosphorous dopants.
Dopants may also be used in the methods discussed with reference to
FIGS. 1-2.
In the reaction chamber, the silicon precursor and the
radical-oxygen precursor mix and react to deposit a
silicon-and-oxygen-containing film on the deposition substrate 306
with trenches formed in its surface. The trenches may have a height
and width that define an aspect ratio (AR) of the height to the
width (i.e., H/W) that is significantly greater than 1:1 (e.g., 5:1
or more, 6:1 or more, 7:1 or more, 8:1 or more, 9:1 or more, 10:1
or more, 11:1 or more, 12:1 or more, etc.). In many instances the
high AR is due to small gap widths that range from about 90 nm to
about 22 nm or less (e.g., about 90 nm, 65 nm, 45 nm, 32 nm, 22 nm,
16 nm, etc.).
The films produced with these methods are initially flowable which
enables them to flow into narrow gaps or trenches and other
structures on the deposition surface of the substrate. The films
flow into gaps with high aspect ratios without creating voids or
weak scams around the center of the filling material. For example,
a depositing flowable material is less likely to prematurely clog
the top of a gap before it is completely tilled to leave a void in
the middle of the gap.
Following the deposition of the silicon-and-oxygen containing film,
a compressive capping layer is deposited over the
silicon-and-nitrogen-containing film 308. One way to deposit a
capping layer under compressive strain is to deposit it with
HDP-CVD similar to the method of depositing the liner layers of
FIG. 1 and the capping layers of FIG. 2. The capping layer may be
made thicker than the lining layers of FIG. 1 and operation 302
since the trenches are largely filled at this point in the process.
Compressive capping layers are integrated into the process flow and
may enable the use of a thinner flowable film due to the additional
material provided by the compressive capping layer. In alternative
embodiments, a liner layer is used without a capping layer and a
capping layer is used without a lining layer.
The film stack is cured in operation 310 to remove some of the
flowing agents left in the film. Any outgassing from the curing
film occurs despite the presence of the compressive capping layer.
A cure step may not be necessary depending on the desired
properties of the final film stack. In other embodiments, the film
is cured in the course of further processing which inevitably
involves some heating of the substrate.
Turning now to discuss general properties of the compressive layers
presented herein, compressive liner layer according to disclosed
embodiments are thinner than half the width of the trenches in
order to allow the subsequently deposited flowable film to flow
into the remaining gap. The thickness of the lining layer may be
less than or about 400 .ANG., less than or about 300 .ANG., less
than or about 200 .ANG. or less than or about 150 .ANG. in
different embodiments. The compressive lining layers must be thick
enough to provide the necessary stability for the trenches and are
thicker than or about 25 .ANG., thicker than or about 50 .ANG.,
thicker than or about 100 .ANG. or thicker than or about 150 .ANG.
in different embodiments. Any of the upper limits may be combined
with any of the lower limits to form additional embodiments.
Compressive capping layers presented herein have more latitude than
the compressive lining layers since they are not constrained by the
width of the substrate trenches. Compressive capping layers may be
thicker than or about 25 .ANG., thicker than or about 50 .ANG.,
thicker than or about 100 .ANG., thicker than or about 200 .ANG.,
thicker than or about 300 .ANG. or thicker than or about 400 .ANG.
in different embodiments. Upper limits on the thickness of the
compressive capping layer are typically determined by a particular
process flow in conjunction with the final thickness of the
flowable layer.
HDP-CVD is one method which may be used to form the compressive
liner and compressive capping layers described herein. During
HDP-CVD deposition, the substrate may be in a separate chamber from
the chamber used to deposit the flowable layer. An exemplary
deposition chamber is the Ultima HDP chamber available from Applied
Materials, Santa Clara, Calif. A substrate may be maintained at
below about 500.degree. C. or between about 300.degree. C. and
about 400.degree. C. during the deposition of compressive films and
the total source plasma RF power applied may be between 5000 Watts
and 10,000 Watts excluding bias power when processing 300 mm wafers
as substrates. The substrate bias power may be between 2000 Watts
and 7000 Watts. Higher bias powers correlate with higher
compressive stress in the liner and capping layers. Chambers other
than the Ultima HDP may be used with conversions in operation
conditions obtainable from processing tool suppliers or may simply
be known to those of ordinary skill in the art. The frequencies
emitted by the non-bias RF power generators may be around 2 MHz,
and the frequency emitted by the bias RF power generator may be
about 13.56 MHz. A variety of oxygen-containing and
silicon-containing sources may be flown into the processing region
during HDP-CVD and typical precursors include O.sub.2 and
SiH.sub.4. In the event that these two precursors are used, a flow
rate ratio for O.sub.2:SiH.sub.4 may be between about 0.25:1 and
about 1:1.
Flowable film growth may proceed while the substrate temperature is
maintained at a relatively low temperature during deposition of the
silicon-containing films (which include nitrogen and/or carbon in
the examples given above. The flowable oxide film may be deposited
on the substrate surface at low temperature which is maintained by
cooling the substrate during the deposition. The pedestal may
include heating and/or cooling conduits inside the pedestal shaft
that set the temperature of the pedestal and substrate between
about -40.degree. C. and about 200.degree. C., between about
100.degree. C. and about 160.degree. C., less than about
100.degree. C. or less than about 40.degree. C. in different
embodiments.
During growth of flowable films, the pressure in either the chamber
plasma region or the substrate processing region may be below or
about 100 Torr, below or about 50 Torr, below or about 20 Torr,
below or about 10 Torr or below or about 5 Torr. The pressures in
either or both regions may be above or about 0.25 Torr, above or
about 0.5 Torr, above or about 1 Torr, above or about 2 Torr or
above or about 5 Torr in different embodiments. Each of the lower
bounds may be combined with any of the upper bounds on the
pressures to form additional ranges of suitable pressures according
to disclosed embodiments.
The plasma conditions present in the chamber plasma region during
the growth of flowable films (to produce radical-oxygen and/or
radical-nitrogen precursors) may include an RF power between about
3000 W and about 15,000 W, between about 400 W and about 10,000 W
or between about 5000 W and about 8000 W in different
embodiments.
Exemplary Substrate Processing System
Embodiments of the deposition systems may be incorporated into
larger fabrication systems for producing integrated circuit chips.
FIG. 4 shows one such system 400 of deposition, baking and curing
chambers according to disclosed embodiments. In the figure, a pair
of FOUPs (front opening unified pods) 402 supply substrate
substrates (e.g., 300 mm diameter wafers) that are received by
robotic arms 404 and placed into a low pressure holding area 406
before being placed into one of the wafer processing chambers
408a-f. A second robotic arm 410 may be used to transport the
substrate wafers from the holding area 406 to the processing
chambers 408a-f and back.
The processing chambers 408a-f may include one or more system
components for depositing, annealing, curing and/or etching a
flowable dielectric film on the substrate wafer. In one
configuration, two pairs of the processing chamber (e.g., 408c-d
and 408e-f) may be used to deposit the flowable dielectric material
on the substrate, and the third pair of processing chambers (e.g.
408a-b) may be used to anneal the deposited dielectric. In another
configuration, the same two pairs of processing chambers (e.g.,
408c-d and 408e-f) may be configured to both deposit and anneal a
flowable dielectric film on the substrate, while the third pair of
chambers (e.g., 408a-b) may be used for UV or E-beam curing of the
deposited film. In still another configuration, all three pairs of
chambers (e.g., 408a-f) may be configured to deposit and cure a
flowable dielectric film on the substrate. In yet another
configuration, two pairs of processing chambers (e.g., 408c-d and
408e-f) may be used for both deposition and UV or E-beam curing of
the flowable dielectric, while a third pair of processing chambers
(e.g. 408a-b) may be used for annealing the dielectric film. It
will be appreciated, that additional configurations of deposition,
annealing and curing chambers for flowable dielectric films are
contemplated b) system 400.
In addition, one or more of the process chambers 408a-f may be
configured as a wet treatment chamber. These process chambers
include heating the flowable dielectric film in an atmosphere that
include moisture. Thus, embodiments of system 400 may include wet
treatment chambers 408a-b and anneal processing chambers 408c-d to
perform both wet and dry anneals on the deposited dielectric
film.
FIG. 5A is a substrate processing chamber 500 according to
disclosed embodiments. A remote plasma system (RPS) 510 may process
a gas which then travels through a gas inlet assembly 511. Two
distinct gas supply channels are visible within the gas inlet
assembly 511. A first channel 512 carries a gas that passes through
the remote plasma system RPS 510, while a second channel 513
bypasses the RPS 500. The first channel 502 may be used for the
process gas and the second channel 513 may be used for a treatment
gas in disclosed embodiments. The lid (or conductive top portion)
521 and a perforated partition 553 are shown with an insulating
ring 524 in between, which allows an AC potential to be applied to
the lid 521 relative to perforated partition 553. The process gas
travels through first channel 512 into chamber plasma region 520
and may be excited by a plasma in chamber plasma region 520 alone
or in combination with RPS 510. The combination of chamber plasma
region 520 and/or RPS 510 may be referred to as a remote plasma
system herein. The perforated partition (also referred to as a
showerhead) 553 separates chamber plasma region 520 from a
substrate processing region 570 beneath showerhead 553. Showerhead
553 allows a plasma present in chamber plasma region 520 to avoid
directly exciting gases in substrate processing region 570, while
still allowing excited species to travel from chamber plasma region
520 into substrate processing region 570.
Showerhead 553 is positioned between chamber plasma region 520 and
substrate processing region 570 and allows plasma effluents
(excited derivatives of precursors or other gases) created within
chamber plasma region 520 to pass through a plurality of through
holes 556 that traverse the thickness of the plate. The showerhead
553 also has one or more hollow volumes 551 which can be filled
with a precursor in the form of a vapor or gas (such as a
silicon-containing precursor) and pass through small holes 555 into
substrate processing region 570 but not directly into chamber
plasma region 520. Showerhead 553 is thicker than the length of the
smallest diameter 550 of the through-holes 556 in this disclosed
embodiment. In order to maintain a significant concentration of
excited species penetrating from chamber plasma region 520 to
substrate processing region 570, the length 526 of the smallest
diameter 550 of the through holes may be restricted by forming
larger diameter portions of through-holes 556 part way through the
showerhead 553. The length of the smallest diameter 550 of the
through-holes 556 may be the same order of magnitude as the
smallest diameter of the through-holes 556 or less in disclosed
embodiments.
In the embodiment shown, showerhead 553 may distribute (via through
holes 556) process gases which contain oxygen, hydrogen and/or
nitrogen and/or plasma effluents of such process gases upon
excitation by a plasma in chamber plasma region 520. In
embodiments, the process gas introduced into the RPS 510 and/or
chamber plasma region 520 through first channel 512 may contain one
or more of oxygen (O.sub.2), ozone (O.sub.3), N.sub.2O, NO,
NO.sub.2, NH.sub.3, N.sub.xH.sub.y including N.sub.2H.sub.4,
silane, disilane, TSA and DSA. The process gas may also include a
carrier gas such as helium, argon, nitrogen (N.sub.2), etc. The
second channel 513 may also deliver a process gas and/or a carrier
gas, and/or a film-curing gas used to remove an unwanted component
from the growing or as-deposited film. Plasma effluents may include
ionized or neutral derivatives of the process gas and may also be
referred to herein as a radical-oxygen precursor and/or a
radical-nitrogen precursor referring to the atomic constituents of
the process gas introduced.
In embodiments, the number of through-holes 556 may be between
about 60 and about 2000. Through-holes 556 may have a variety of
shapes but are most easily made round. The smallest diameter 550 of
through holes 556 may be between about 0.5 mm and about 20 mm or
between about 1 mm and about 6 mm in disclosed embodiments. There
is also latitude in choosing the cross-sectional shape of
through-holes, which may be made conical, cylindrical or a
combination of the two shapes. The number of small holes 555 used
to introduce a gas into substrate processing region 570 may be
between about 100 and about 5000 or between about 500 and about
2000 in different embodiments. The diameter of the small holes 555
may be between about 0.1 mm and about 2 mm.
FIG. 5B is a bottom view of a showerhead 553 for use with a
processing chamber according to disclosed embodiments. Showerhead
553 corresponds with the showerhead shown in FIG. 5A. Through-holes
556 are depicted with a larger inner-diameter (ID) on the bottom of
showerhead 553 and a smaller ID at the top. Small holes 555 are
distributed substantially evenly over the surface of the
showerhead, even amongst the through-holes 556 which helps to
provide more even mixing than other embodiments described
herein.
An exemplary film is created on a substrate supported by a pedestal
(not shown) within substrate processing region 570 when plasma
effluents arriving through through-holes 556 in showerhead 553
combine with a silicon-containing precursor arriving through the
small holes 555 originating from hollow volumes 551. Though
substrate processing region 570 may be equipped to support a plasma
for other processes such as curing, no plasma is present during the
growth of the exemplary film.
A plasma may be ignited either in chamber plasma region 520 above
showerhead 553 or substrate processing region 570 below showerhead
553. An AC voltage typically in the radio frequency (RF) range is
applied between the conductive top portion 521 of the processing
chamber and showerhead 553 to ignite a plasma in chamber plasma
region 520 during deposition. The top plasma is left at low or no
power when the bottom plasma in the substrate processing region 570
is turned on to either cure a film or clean the interior surfaces
bordering substrate processing region 570. A plasma in substrate
processing region 570 is ignited by applying an AC voltage between
showerhead 553 and the pedestal or bottom of the chamber. A
cleaning gas may be introduced into substrate processing region 570
while the plasma is present.
The substrate processing system is controlled by a system
controller. In an exemplary embodiment, the system controller
includes a hard disk drive, a floppy disk drive and a processor.
The processor contains a single-board computer (SBC), analog and
digital input/output boards, interface boards and stepper motor
controller boards. Various parts of CVD system conform to the Versa
Modular European (VME) standard which defines board, card cage, and
connector dimensions and types. The VME standard also defines the
bus structure as having a 16-bit data bus and a 24-bit address
bus.
The system controller controls all of the activities of the CVD
machine. The system controller executes system control software,
which is a computer program stored in a computer-readable medium.
Preferably, the medium is a hard disk drive, but the medium may
also be other kinds of memory. The computer program includes sets
of instructions that dictate the timing, mixture of gases, chamber
pressure, chamber temperature, RF power levels, susceptor position,
and other parameters of a particular process. Other computer
programs stored on other memory devices including, for example, a
floppy disk or other another appropriate drive, may also be used to
instruct the system controller.
A process for depositing a film stack on a substrate or a process
for cleaning a chamber can be implemented using a computer program
product that is executed by the system controller. The computer
program code can be written in any conventional computer readable
programming language: for example, 68000 assembly language, C, C++,
Pascal, Fortran or others. Suitable program code is entered into a
single file, or multiple files, using a conventional text editor,
and stored or embodied in a computer usable medium, such as a
memory system of the computer. If the entered code text is in a
high level language, the code is compiled, and the resultant
compiler code is then linked with an object code of precompiled
Microsoft Windows.RTM. library routines. To execute the linked,
compiled object code the system user invokes the object code,
causing the computer system to load the code in memory. The CPU
then reads and executes the code to perform the tasks identified in
the program.
The interface between a user and the controller is via a flat-panel
touch-sensitive monitor. In the preferred embodiment two monitors
are used, one mounted in the clean room wall for the operators and
the other behind the wall for the service technicians. The two
monitors may simultaneously display the same information, in which
case only one accepts input at a time. To select a particular
screen or function, the operator touches a designated area of the
touch-sensitive monitor. The touched area changes its highlighted
color, or a new menu or screen is displayed, confirming
communication between the operator and the touch-sensitive monitor.
Other devices, such as a keyboard, mouse, or other pointing or
communication device, may be used instead of or in addition to the
touch-sensitive monitor to allow the user to communicate with the
system controller.
As used herein "substrate" may be a support substrate with or
without layers formed thereon. The support substrate may be an
insulator or a semiconductor of a variety of doping concentrations
and profiles and may, for example, be a semiconductor substrate of
the type used in the manufacture of integrated circuits. A gas in
an "excited state" as used herein describes a gas wherein at least
some of the gas molecules are in vibrationally-excited, dissociated
and/or ionized states. A gas may be a combination of two or more
gases. The term trench is used throughout with no implication that
the etched geometry necessarily has a large horizontal aspect
ratio. Viewed from above the surface, trenches may appear circular,
oval, polygonal, rectangular, or a variety of other shapes.
Having described several embodiments, it will be recognized by
those of skill in the art that various modifications, alternative
constructions, and equivalents may be used without departing from
the spirit of the invention. Additionally, a number of well-known
processes and elements have not been described in order to avoid
unnecessarily obscuring the present invention. Accordingly, the
above description should not be taken as limiting the scope of the
invention.
Where a range of values is provided, it is understood that each
intervening value, to the tenth of the unit of the lower limit
unless the context clearly dictates otherwise, between the upper
and lower limits of that range is also specifically disclosed. Each
smaller range between any stated value or intervening value in a
stated range and any other stated or intervening value in that
stated range is encompassed. The upper and lower limits of these
smaller ranges may independently be included or excluded in the
range, and each range where either, neither or both limits are
included in the smaller ranges is also encompassed within the
invention, subject to any specifically excluded limit in the stated
range. Where the stated range includes one or both of the limits,
ranges excluding either or both of those included limits are also
included.
As used herein and in the appended claims, the singular forms "a",
"an", and "the" include plural referents unless the context clearly
dictates otherwise. Thus, for example, reference to "a process"
includes a plurality of such processes and reference to "the
precursor" includes reference to one or more precursor and
equivalents thereof known to those skilled in the art, and so
forth.
Also, the words "comprise," "comprising," "include," "including,"
and "includes" when used in this specification and in the following
claims are intended to specify the presence of stated features,
integers, components, or steps, but they do not preclude the
presence or addition of one or more other features, integers,
components, steps, acts, or groups.
* * * * *